The invention relates to a method and system for regenerating a soot particle filter.
Soot particle filters or diesel particle filters (DPF) for internal combustion engines of motor vehicles are known from the general prior art. As an indicator for a particle quantity situated in the DPF, use is normally made of a differential pressure corresponding to the pressure loss across the DPF, wherein, when a predetermined differential pressure is reached, a regeneration process of the DPF is started. For the regeneration, it is common for the DPF to be supplied with exhaust gas from the internal combustion engine with a high exhaust-gas temperature, and for an oxidation of the particles situated in the DPF to thus be initiated. However, if no regeneration is initiated in the presence of the predetermined differential pressure, for example because the required exhaust-gas temperatures cannot be realized, such as is the case in internal combustion engines of motor vehicles over short journeys, the quantity of particles situated in the DPF increases further. This can lead to a regeneration no longer being possible during driving operation, because the thermal energy content of the particles is then so great that an uncontrolled oxidation of the particles could lead to thermal destruction of the soot particle filter. The regeneration of the DPF is then normally blocked by a control system, and the DPF must be exchanged. This is generally associated with high costs, and shortens the service life of the DPF.
DE 10 2007 034 709 A1 discloses an exhaust-gas purification device with a diesel particle filter (DPF). The exhaust-gas purification device has a regeneration device for performing a regeneration of the DPF. The regeneration device performs a first regeneration until a predetermined time point which is configured in accordance with a value of a decision parameter, for example the differential pressure across the DPF. During the first regeneration, the temperature in the DPF is detected, and the maximum temperature reached is determined. On the basis of the maximum temperature reached, the decision parameter is corrected such that a second regeneration of the filter occurs at a later or earlier time point, that is to say in the presence of a greater or lesser differential pressure. In the case of this exhaust-gas purification device, a flexible criterion is specified for the regeneration time point. However, even with this, overloading of the filter cannot reliably be prevented under all circumstances.
It is an object of the invention to provide a method and a system for regenerating a soot particle filter, with which each case the service life of the soot particle filter is improved and the latter can be regenerated in an economically advantageous manner.
According to the invention, a method is provided for regenerating a soot particle filter of an internal combustion engine, in particular of an internal combustion engine of a motor vehicle, wherein, from a differential pressure signal received from a differential pressure sensor, an engine control unit determines a pressure difference which prevails between an exhaust-gas inlet and an exhaust-gas outlet of the soot particle filter with a differential pressure sensor detected pressure difference and is proportional to a particle quantity situated in the soot particle filter, and the engine control unit compares the pressure difference with a pressure difference threshold value in order to operate the internal combustion engine in a regeneration operating profile if the determined pressure difference is smaller than the pressure difference threshold value, wherein, if the determined pressure difference is greater than the pressure difference threshold value, manual electrical connection of a differential pressure correction device between the differential pressure sensor and the engine control unit is performed, and, by means of the differential pressure correction device, generation of a differential pressure simulation signal is performed, in the case of which the engine control unit determines a pressure difference which is smaller than the pressure difference threshold value, in order to operate the internal combustion engine in the regeneration operating profile.
By means of the connection of the differential pressure correction device, it is possible for a regeneration of the soot particle filter to be performed without modifying the regulation processes of the engine control unit. The connection may be performed for example during maintenance work on the engine or on the soot particle filter.
By means of the generation of the differential pressure simulation signal using the differential pressure correction device, a regeneration of the particle filter, which is no longer permitted per se by the engine control unit on the basis of the comparison of the determined pressure difference with the pressure difference threshold value, is made possible again or re-enabled. In this way, the service life of the soot particle filter is lengthened, because in this way, a greater number of regeneration cycles can be performed.
The differential pressure simulation signal may be generated in particular by multiplication of the differential pressure signal by a correction factor.
Here, the correction factor may advantageously be defined in a manner dependent on the detected pressure difference. In particular, a regional dependency is advantageous. For example, the correction factor may have a value less than the magnitude 1, such that, in the event of connection of the differential pressure correction device, the pressure difference determined by the differential pressure sensor is smaller than the respectively predefined pressure difference threshold value. Furthermore, it is provided in particular that, in an operating state in which the respectively determined pressure difference is smaller than or equal to the respectively predefined pressure difference threshold value, the correction factor is a factor with a magnitude equal to 1.
By means of a regional dependency of the correction factor on the detected pressure difference and, alternatively or in addition to this, on the pressure difference threshold value, a complete regeneration cycle can be performed with a connected or interconnected differential pressure correction device, because the correction factor actually performs a correction of the detected pressure difference for example only for as long as the detected pressure difference is greater than the pressure difference threshold value. If the latter is undershot during the regeneration, although the differential pressure simulation signal then continues to be generated, this then however represents the detected pressure difference.
It may furthermore be provided that the engine control unit operates the internal combustion engine in a general operating profile if a regeneration end criterion is attained for the determined pressure difference.
The regeneration end criterion may be defined as a fixed value of the pressure difference, that is to say as a regeneration end value. When the regeneration end value DPr is attained, it is assumed that no particles, or else only a small quantity of particles, are/is situated in the soot particle filter. It is also conceivable for the regeneration end criterion to be defined as a rate of change of the detected pressure difference with respect to time. As an alternative to this, the regeneration criterion may be defined in that the magnitude of the determined pressure difference changes by less than a minimum magnitude in a predetermined time interval, or the ratio of the magnitude of the determined pressure difference at the end of the predetermined time interval to the magnitude of the determined pressure difference at the start of the time interval is smaller than a particular threshold value, the magnitude of which is for example smaller than 0.1. When the regeneration end criterion is attained, the regeneration of the filter is ended.
The connection or interconnection of the differential pressure correction device may be performed in particular by virtue of a first connection device of the differential pressure correction device being connected to a signal output of the differential pressure sensor and a second connection device of the differential pressure correction device being connected to a signal input of the engine control unit.
By means of the interconnection by way of a plug-in connection, it is ensured that the method can be carried out in a particularly straightforward manner. This additionally increases the cost-effectiveness of the method. The plug-in connections may additionally be designed to be protected against polarity reversal. Incorrect implementation of the method is thus ruled out.
According to the invention, a system for regenerating a soot particle filter of an internal combustion engine is also provided. The system has:
an internal combustion engine,
a soot particle filter arranged in an exhaust-gas section of the internal combustion engine,
a differential pressure sensor which detects a pressure difference between an exhaust-gas inlet and an exhaust-gas outlet of the soot particle filter,
an engine control unit which, from a differential pressure signal received from a differential pressure sensor, determines a pressure difference and which compares the pressure difference with a predefined pressure difference threshold value and which operates the internal combustion engine in a regeneration operating profile if the determined pressure difference is smaller than the pressure difference threshold value and greater than the pressure difference threshold value,
a pressure difference correction device which is connected in a functionally decoupleable manner to the differential pressure sensor and to the engine control unit,
wherein the differential pressure correction device has a differential pressure correction function which generates a differential pressure simulation signal, wherein the engine control unit determines, from the differential pressure simulation signal, a pressure difference which is smaller than the pressure difference threshold value, such that the engine control unit operates the internal combustion engine in the regeneration operating profile.
The determined pressure difference is proportional to a particle quantity situated in the soot particle filter.
By virtue of the fact that the differential pressure correction device is designed to be functionally decoupled, that is to say for example capable of being plugged in and unplugged, the system is easy to handle. By means of the connection or interconnection of the differential pressure correction device, it is possible to perform a regeneration of the soot particle filter without modifying the regulation processes of the engine control unit. Thus, the system can be easily retrofitted in motor vehicles with a soot particle filter.
In the system, it may be provided in particular that the correction function of the differential pressure correction device generates the differential pressure simulation signal by multiplication of the differential pressure signal by a correction factor.
Here, the correction factor may be regionally dependent on the determined pressure difference.
The advantages of such a configuration of the correction factor have already been described above on the basis of the method according to the invention, and are achieved analogously with the system according to the invention.
It may furthermore be provided that the engine control unit sets a general operating state of the internal combustion engine if a regeneration end criterion is attained for the determined pressure difference.
The definitions of the regeneration end criterion given with regard to the method apply analogously to the system according to the invention.
It may be advantageous that the differential pressure correction device is connected by virtue of a first connection device of the differential pressure correction device being coupleable to a signal output of the differential pressure sensor and a second connection device of the differential pressure correction device being coupleable to a signal input of the engine control unit.
The coupling may be realized for example by means of a plug-in connection. Coupling by means of wireless data transmission is also possible.
Here, the expressions “laden state” and “filled state” are each to be understood generally to mean a state of the soot particle filter in which, in the soot particle filter, there is situated a particle quantity, for example a particular mass of soot, dust or other particles, which is greater than or equal to a maximum admissible particle quantity. The maximum admissible particle quantity gives rise to a pressure loss in a flow, in particular an exhaust-gas flow, from the exhaust-gas inlet to the exhaust-gas outlet of the soot particle filter, which pressure loss is greater than or equal to a maximum admissible value for the pressure loss, in particular a pressure difference threshold value.
Here, the expression “regeneration of the soot particle filter” is to be understood generally to mean the removal of particles situated in the soot particle filter, in particular by oxidation of the particles, in particular during an oxidation triggered by the thermal and stoichiometric conditions in the exhaust gas.
Here, the expressions “overladen state” or “overloaded state” are each to be understood generally to mean a laden state of the soot particle filter in the case of which, in the soot particle filter, there is situated a particle quantity, for example a particular mass of soot, dust or other particles, which has a thermal energy content which could lead to thermal destruction of the soot particle filter in the event of uncontrolled oxidation of the particles. In the overladen state, the particle quantity gives rise to a pressure loss in the flow from the exhaust-gas in that the exhaust-gas outlet of the soot particle filter, which pressure loss is greater than a pressure difference threshold value.
Here, the expression “regenerated state” is to be understood generally to mean a state of the soot particle filter in which, in the soot particle filter, there is situated a particle quantity, for example a particular mass of soot, dust or other particles, which gives rise to a pressure loss in a flow, in particular an exhaust-gas flow, from the exhaust-gas inlet to the exhaust-gas outlet of the soot particle filter, which pressure loss is smaller than the admissible value for the pressure loss, and in the presence of which pressure loss the regeneration end criterion is attained.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
Exemplary embodiments of the invention will be described below on the basis of the drawings.